The House of Húrin was founded by Húrin of Emyn Arnen who was Steward to King Minardil and after his death the Kings chose their Stewards exclusively from his descendants. In T.A. 1998 the Stewardship became hereditary in the House of Húrin following the death of Pelendur.
The Stewards rose in prominence during the days of the last Kings who came to rely on them increasingly as a kind of Chief Minister. After the last King of Gondor died without an heir, the House of Húrin ruled Gondor for 969 years until the heir of Isildur from the House of Elendil, Aragorn, again reclaimed the Throne after the War of the Ring.